The ThinkCentre M92p system contains a provision for an additional port just above the VGA display connector on the rear of the unit. In the first photo below, there is a stack of 3 M92p Tiny systems mounted in the optional optical drive chasis. This drive enclosure connects via a USB loop cable and provides two additional USB ports in addition to the optical drive which would also be installed.
The system appearing at the top of the stack below has a knock out cover in place above the VGA connector - no optional port installed. The second unit has an optional wifi card and dual antennas with the second antenna occupying this port location. The unit on the bottom of the stack has the optional 2nd display port option.
While service part numbers can be found in thehardware maintenance manual for USB port, serial port, and 2nd display port connectors and cables that can be installed in this location above the VGA port, it appears that there are at least 2 versions of the system board which differ slightly in component locations, and whether the header connector for the 2nd display port is populated on the board. Both versions of the board have the header for the serial connector.
The version in the photo below would not support the 2nd display port cable because the connector on the system board has not been populated. Note the empty solder pads at the location indicated by the red arrow. If you are considering adding a 2nd display port, check your system to see if there is a socket at this location on the system board.
The version show in the photo below shipped with the 2nd display port option and includes the connector socket on the system board (see arrow). Cable display port assembly FRU 54Y9350 is shown, to the right of the arrow.
So, it appears that the second display port would need to be ordered when the system was built, while a serial port could be added to replace the blank port simply by ordering the cable as a FRU.
The wifi card options and antenna parts are also listed in the HMM. Here is an inside view of the wifi card installed.